Wheel slip control means



April 23, 1 940.

C. C. FARMER WHEEL SLIP CONTROL MEANS FiledMay 24, 1938 3 Sheets-Sheet -1 INVENTOR CLYDE C. FAHMER M ATTORNEY 4% mm M 3 i am 5w April 23, 1940. c. c. F'ARMER 2,198,029

WHEEL SLIP CONTROL MEANS Filed May 24, 1938 3 Sheets-sheaf 2 Z 54 rm I6 64- e5 77 INVENTOR CLYDE C. FARMEH BY ATTORNEY April 23, 1940. c, c, FARMER WHEEL SLIP CONTROL MEANS Filed May '24, 1938 3 Sheets-Sheet 3 m2 +2 m2 SN 2 INVENTOR CLYDE Q AHMER" I M,L.

ATTORNEY Patented Apr. 23, 1940 UNHTED STATES PATENT OFFICE WHEEL SLIP CONTROL NIEANS Application May 24, 1938, Serial No. 209,648

24 Claims. (01. 303-21) This invention relates to wheel-slip control means for vehicles, such as railway cars or trains, and particularly to vehicle brake systems having control means automatically responsive to the slipping of an individual wheel and axle unit for releasing the brakes on the slipping wheels to prevent sliding thereof.

As is well known, when the brakes associated with a vehicle wheel are applied with suflicient force to exceed the limit of adhesion between the treador rim of the wheel and the road surface or rail, the wheel rapidly decelerates toward a locked or non-rotative condition. If the braking force on a slipping vehicle wheel is rapidly reduced at the intent that a Wheelbeg'lns to slip, the vehicle wheel will cease to decelerate and accelerate back toward a rotative speed corresponding to vehicle speed without actually attaining the locked or non-rotative condition.

For convenience, the term slip or slipping is applied herein to the rotation of a vehicle wheel at a speed less than a rotative speed corresponding to vehicle speed at a given instant, whether the wheel is decelerating or accelerating. The term slide or .sliding is employed herein to designate the dragging of a vehicle wheel along a road surface or rail in a locked or non-rotative state. Thus it should be understood that a slipping wheel is one which is rotating whereas a sliding wheel is one which is not rotating.

In order to minimize the possibility of repeated slipping cycles of deceleration and acceleration with respect to a speed corresponding to vehicle speed, it is desirable to avoid the reapplication of the brakes on a slipping wheel until it returns fully to a speed corresponding to vehicle speed.

Various types of brake control equipment for this purpose have been proposed, including that I described and claimed in my copending application Serial No. 137,956, filed April 20, 1937, now Patent 2,140,620.

My present invention comprises a novel controlarrangement'for preventing the reapplication of the brakes on a slipping wheel until it has attained a rotative speed corresponding substantially to a speed corresponding to vehicle speed. The principle of operation of the control equipment of my invention is based on the fact that deceleration of a slipping wheel can be stopped and'acceleration thereof back toward a speed corresponding to vehicle speed produced in response to a relatively small amount of reduction in the braking force from that which initiated the slipping of the Wheel when the reduction is efiected rapidly and substantially at the instant that the wheel begins to slip.

My invention includes a fluid pressure responsive device normally unresponsive to the pressure in the brake cylinder associated with a particular vehicle wheel, and a device which is instantly responsive to the slipping of the wheel for causing the fluid pressure responsive device to be operated to effect release of fluid under pressure from the brake cylinder, the fluid pressure device being thereafter so controlled by the pressure in the brake cylinder that the reduction of brake cylinder pressure to a certain low value is guaranteed independently of subsequent variations in the rotative condition of the vehicle wheel. When the brake cylinder pressure is reduced below the certain low pressure, the fluid pressure responsive device is operative to cause fluid under pressure to be resupplied to the brake cylinder to effect reapplication of the brakes.

By thus guaranteeing or insuring the reduction of brake cylinder pressure to a relatively low pressure, the reapplication of the brakes is held ofi while the vehicle wheel is accelerating back toward a speed corresponding to vehicle speed. Such holding off of the reapplication of the brakes is in most cases suificient to permit the return'of the slipping wheel fully to a speed corresponding to vehicle speed before reapplication of the brakes is eflected.

Ii theiriction in the brake rigging of a conventional clasp brake is high, as is sometimes the case, the braking force applying the brake shoes is not instantly reduced upon reduction of brake cylinder pressure so that it may sometimes be necessary to reduce the brake cylinder pressure to a low value in order to cause release of the brakes so that a slipping wheel may begin to accelerate back toward a speed corresponding to vehicle speed. Accordingly, by guaranteeing the reduction of brake cylinder pressure to a low value, my invention positively insures the cessation of deceleration of a slipping wheel and its acceleration back toward a speed corresponding to vehicle speed.

Furthermore, if the adhesion between a car wheel and rail is low, the acceleration of a slipping wheel back toward a speed corresponding to .vehicle speed will be at a slower rate than when the adhesion between the wheel and the rail is high. Thus, due to variation in brake rigging friction and to variation in the adhesion between the Wheel and the rail the time interval elapsing between the instant that a vehicle wheel begins to slip and the instant that it returnsto a speed corresponding substantially to vehicle speed will vary. In order therefore to insure that the slipping vehicle wheel will return fully to a speed corresponding to vehicle speed before any substantial degree of reapplication of the brakes is effected thereon, my invention also provides for restricting the rate of reapplication of the brakes on a slipping Wheel.

It is accordingly an object of my invention to provide a vehicle brake equipment including means effective, once a vehicle wheel begins to slip, for insuring or guaranteeing the reduction in the braking force or brake cylinder pressure to a relatively low degreeso as to prevent the reapplication of the brakes on the slipping wheel until the slipping wheel returns substantially to a speed corresponding to vehicle speed, and also so as to insure the cessation of deceleration of a slipping wheel and its acceleration back toward a speed corresponding to vehicle speed.

Another object, of my invention is to provide a vehicle brake equipment including means automatically effective, once a vehicle wheel slips, to restrict the rate of reapplication of the brakes on the slipping wheel.

Another object of my invention is to provide a vehicle brake equipment of the character indicated in the foregoing object in which the means for controlling the rate of reapplication of the brakes on a slipping wheel is operated and controlled by fluid under pressure vented from the brake cylinder associated with a slipping wheel.

The above objects, and other objects of my invention which will be made apparent in the subsequent description thereof, are attained by several embodiments shown in the accompanying drawings, wherein,

Fig. 1 is a simplified diagrammatic View of a brake equipment embodying my invention,

Figs. 2, 3 and 4 are fragmentary views showing various other embodiments of my invention respectively, which differ somewhat from the arrangement shown in Fig. 1,

Fig. 5 is a fragmentary diagrammatic View illustrating a preferred embodiment of my invention which differs from the previous embodiments in providing means for controlling the rate of reapplication of brakes on a slipping wheel.

Description of embodiment shown in Fig. 1

Before proceeding to a detailed description of my invention, it should be understood that, for simplicity, the various embodiments shown and described herein include only those elements necessary to an understanding of my invention but that, in practice, my invention will be applied to brake control systems for modern high speed trains employing governor devices operative according to the speed of the train or retardation controller devices responsive to the rate of retardation of the train for automatically reducing the degree of application of the brakes on the train as the speed of the train reduces under an application of the brakes. Examples of such modern high speed train brake equipment are described and claimed in the Patents 2,147,295 and 2,140,624 of Ellis E. Hewitt.

It should accordingly be understood that as distinguished from such types of brake control systems wherein the degree of a brake application on all wheel and axle units of a train of cars is controlled simultaneously and uniformly, the apparatusof my present invention controls the brakes on an individual pair or pairs of wheel and axle units. Thus a complete brake equipment may provide automatic control of the brakes on all wheel and axle units by means of a speed governor or retardation controller device in addition to the control of individual wheel and axle units by the apparatus of my present invention, and this is an important fact to bear in mind in the subsequent description of the operation of my invention, as will be made more apparent hereinafter.

Referring to Fig. 1, the equipment shown comprises a brake cylinder II for effecting application and release of the brakes associated. with one or more vehicle wheels, not shown, a source of fluid under pressure such as a main reservoir I2, and a manually operated brake valve device I3 for controlling the supply of fluid under pressure from a supply pipe It, connected to the main reservoir I2, to a so-called straight air pipe I5 leading to the piston chamber in the brake cylinder II. The equipment also includes, according to my invention, a release and reapplication valve device I6, hereafter referred to as the release valve, interposed in the straightair pipe l5, a magnet valve device I I for controlling the operation of the release valve I 6, a fluid pressure operated switch device I8 for controlling the magnet valve device I'I, a magnet valve device IQ for in part controlling the operation of the fluid pressure operated switch device I8, a Wheel-slip responsive device 2| associated with one of the wheels with which the brake cylinder II is associated, a pressure-operated switch 22 for controlling both the magnet valve devices I! and I9, and a source of electric current indicated as a storage battery 23.

Considering the parts of the equipment in greater detail, the brake valve I3 is of a selflapping type, such as described and claimed in Patent 2,042,112 of Ewing K. Lynn and Rankin J. Bush. The details of construction of the brake valve I3 are not necessary to an understanding of my invention and accordingly it is described herein only functionally. When the operating handle 25 of the brake valve I3 is in its normal release position, the brake valve device I3 vents the straight-air pipe I5 to atmosphere. When the handle 25 is shifted horizontally into a so-called application zone out of its normal release position, the brake valve I3 establishes communication through which fluid under pressure is supplied from the supply pipe Hi to the straight-air pipe I5, the brake valve I3 being automatically self-lapping to establish a pressure in the straight-air pipe I5 substantially proportionate to the degree of displacement of the operating handle out of its normal release position. Should the pressure in the straight-air pipe I5 tend to reduce, due to leakage, from a pressure corresponding to the position of the operating handle, the brake valve I3 is automatically operative to supply further fluid under pressure to the straight-air pipe. The purpose and the utility of this pressure-maintaining feature of the self-lapping brake valve I3 will be made apparent hereinafter.

The release valve I6 is of well known construction being of a conventional type employed in modern high speed railway brake equipment. The purpose of the release valve is, briefly, to close communication through the straight-air pipe I5 and vent fluid under pressure from the brake cylinder II at a rapid rate.

The release valve I6 comprisesasectionalized iii) casing containing a piston valve 21 and an operating piston 28 connected to the valve 21 by a stem 29. Formed between the operating piston 28' and the end or cover section 3| of the casing that closes the bore in which the piston 28 operates is a chamber 32. Contained in the chamber 32 in interposed relation between the operating piston 23 and the casing section 3| is a coil spring 33 which is efiective normally to urge the piston downwardly so as to cause a gasket 34 inset in the face of the piston valve 21 to seat on an annular rib seat 35 which surrounds an exhaust or vent port 38.

With the piston valve 21 seated on the annular rib seat 35, one portion of the straight-air pipe l5 leading from the brake valve l3 and the other portion of the straight-air pipe l5 leading to the brake cylinder H are connected into the annular chamber 31 formed between the operatingpiston 28 and the piston valve 21. Accordingly, with the piston valve 21 positioned as shown in the drawings, fluid under pressure may be supplied or released through the straight-air pipe l5 to and from the brake cylinder 1 I under the control of brake valve [3. I

The chambers 32 and 31 on opposite sides of the operating piston 28 are connected through a restricted port 38 in the operating piston. Thus, if fluid under pressure is prevented from flowing out of the chamber 32, chamber 32 becomes charged rapidly by flow of fluid under pressure from the chamber 29 through the port 38 in the operating piston 28 so that, while a certain differential pressure is produced momentarily on the piston in the chambers 31 and 32, nevertheless such pressure differential is insufiicient to cause upward movement of the operating piston and unseating of piston valve 3'! from the an nular rib seat 35.

ing piston 28 is subject to the pressure of fluid supplied into the straight-air pipe l5 and acting on the lower face of the operating piston 28 in the chamber 31, the differential force of the pressure in chamber 31 over that in the chamber 32 lifts the piston 23 upwardly against the yielding resisting force of the spring 33 and accordingly unseats the piston valve 2'! from the annular rib seat 35.

When shifted upwardly, the operating piston 28 seats on an annular gasket 39 supported on the casing section 3|. With the operatingpiston 28 in its raised position in contact with the annular gasket 39, the piston valve 2? is correspondingly shifted upwardly to a point between the openings of two portions of the straight-air pipe l5 into chamber 3'5, thus effectively closing communication through which fluid under pressure may be supplied from the brake valve E3 to the brake cylinder H and at the same time opening the portion of the straight-air pipe it, connected to the brake cylinder, to atmosphere through the exhaust port 36.

If the chamber 32 continues to be vented, the continued supply of fluid under pressure from the brake-valve l3 to the annular chamber 3'! beneath the operating piston 28 'holds the operating piston in contact with the annular gasket seat 39 and thus maintains the piston valve 2'! r in its raised position so that venting of fluid under pressure from the brake cylinder continues.

This is a feature which should be kept in mind in the later description of the operation of my invention Magnet valve device I! is provided for eifect- I However, if the pressure in chamber 32 is suddenly reduced while the operating reduction of pressure in the chamber 32 of the application valve device it. Briefly, magnet valve [1 comprises a casing containing a valve 42 of the poppet type which is seated under the influence of a. coil spring 43 and unseated against the force of the spring 43 by the magnetic force exerted on a plunger 44 upon energization of a solenoid or electromagnet winding 45 associated with the plunger. The valve 42 is contained in a chamber 46 which is constantly connected through a pipe and passage 61 to the chamber 32 of the application valve device It. The valve 42 has a fluted stem 48 which extends slidably energized, the valve 42 is seated by the spring 43, thus preventing the escape or fluid under pressure from the piston chamber 32v of the.application valve I 6. It will also be seen that when the electromagnet winding 45 of the magnet valve i1 is energized and the valve 42 consequently unseated, the chamber 32 of the application valve lfi is connected to atmosphere and fluid under pressure is vented therefrom through the exhaust port 5! of themagnet valve 11.

Fluid pressure operated switch 113 is provided for controlling energization and deenergization of the electromagnet winding 35 of the magnet valve device ll. As diagrammatically shown in Fig. l, the switch device 18 comprises a casing having a bore 53 containing a loose-fitting piston 54 which is effective to operate a movable switch member 55 and a valve 53 of the poppet type. As illustrated, the switch member 55 is .carried in insulated relation on a stem 53 of the piston 55 and valve tfiis formed or carried on the end of a stem 5'! on the opposite side of the piston 34 to the stem 5t.

Interposed between the casing and the upper face of the piston 54 within a chamber 5?; that is constantly connected to atmosphere through a port 59, is a coil spring 6i which urges the piston 54 downwardly to a position in which the switch member 55 disengages a pair of associated stationary contact members 62, suitably supported by the casing in a manner not shown, and in which the valve 56 seats on an associated valve seat formed on the end casing section 63 that closes the open end of the bore 53.

Valve 56 controls communication between a' chamber 6 1, iormed between the piston 54 and the casing section 33, and that portion of the straight-air pipe l5 connecting the release valve It to the brake cylinder l l, a branch pipe and passage 65 being provided to connect the straightair pipe I 5 to the. chamber 6t of switch device It,

Spring 3! is of such strength as to normally maintain the valve 53 seated and the switch member 55 in circuit-opening position out of contact with the contact members 32 against the maximum force of the fluid pressure in'the straight-air pipe 15 acting on the inner seated area of the valve 56 and tending to unseat the valve 56. However, if fluid under pressure is supplied independently of valve 53 to the chain: ber 64, the force exerted on the relatively large area of the piston 54 is effective to overcome the resisting force of the spring ti and shift the piston 54 upwardly to unseat the valve 53 and shift the switch member 55 into contact with the contact members 62.

It will be seen, therefore, that normally the pressure of the fluid in the brake cylinder l i and straight-air pipe i5 is ineffective to cause shifting of the switch member 55 into circuit-closing position and that after the switch member 55 is once shifted into circuit-closing position and the valve 56 unseated, the pressure in the brake cylinder and straight-air pipe iii is effective to maintain the piston 54 in raised position so as to maintain the switch member 55 in circuitclosing position.

The strength of the spring 5! is so designed in relation to the area of the piston 54 that the pressure in the straight-air pipe I5 and brake cylinder I I acting on the piston 54 will maintain the switch member 55 in circuit-closing posi tion unless and until the pressure in the brake cylinder or straight-air pipe reduces below a certain uniform low pressure, such as fiVE) pounds per square inch.

The piston 54 is made to have a loose fit in the bore 53 to permit the escape of fluid under pressure past the piston from the chamber 66 to the atmospheric chamber 58 in the event of leakage past the valve from the straight-air pipe I5, so that undesired build-up of pressure in chamber 64 and the consequent undesired operation of the switch member to circuit-closing position is prevented.

It will be seen, therefore, that in order to initially effect operation of the switch member 55 of the switch device 99 to circuit-closing position, it is necessary to first supply fluid under pressure to the chamber 36 of the switch device It, and the magnet valve E0 is accordingly provided for this purpose.

The magnet valve I9 is similar to the magnet valve I1 and comprises a suitable casing contain ing a valve I2 yieldingly biased into seated relation on an associated valve seat by a coil spring 13 and unseated by the magnetic force exerted on a plunger 14 when an electromagnet winding or solenoid associated with the plunger "I4 is energized. Valve 72 is contained in a chamber 16 which is constantly connected through a branch pipe and passage 71 to the straight-air pipe I5 at a point adjacent the brake cylinder II. The fluted stem 78 of the valve 12 extends slidably through a suitable bore connecting the chamber 76 and a chamber I9 that is constantly connected to the chamber 64 of the switch device I8 by a pipe 8|.

It will accordingly be seen that when the electromagnet winding 15 of the magnet valve I9 is energized and the valve 12 unseated, fluid under pressure is supplied from the straight-air pipe I5 and the connected brake cylinder II to the chamber 6 3 of the switch device I8 and that when the electromagnet 15 is deenergized such supply is cut off due to the seating of the valve 12.

The wheel-slip responsive device 2| is provided for controlling energization and deenergization of the electromagnet winding I5 of the magnet valve I9. Any suitable type of wheel-slip responsive device maybe provided and, for purposes of illustration, a wheel-slip responsive device of the type described in detail and claimed in my abovereferred to Patent 2,140,620 is shown.

The wheel-slip responsive device 2| comprises a tubular casing in which is contained a rotary inertia element in the form of a fly-wheel 86, a driving shaft 81 for the fly-Wheel, and a switch device 88. The driving shaft 81 is supported at opposite ends thereof by ball bearings 89, one of the bearings being contained in the endv cover 9| of the casing 85 and the other of the bearings being slidably supported within a bore 92 in the laterally projecting hub portion 93 of the flywheel 80.

The fly-wheel 85 is supported for rotation within the casing by a ball bearing 94 at the end of the hub portion 93 which bearing is arranged to move slidably in a bore 95 of the casing, and by another ball bearing 96 at the opposite .end of the hub portion in a suitable recess in the face of the fly-wheel which bearing is arranged to rotatably and slidably support the fiy-wheel on the shaft 81.

Suitably fixed to the outer end of the shaft 81 which projects through the end cover SI of the casing is a pulley I 0| having an anular groove I02 therein for receiving an endless belt which is driven in any suitable manner according to the rotation of one of the vehicle wheels on which the brakes are applied by the brake cylinder II.

The shaft 81 may be driven directly from the axle of the wheel by means of an endless belt or, indirectly, from any other element rotative according to the rotation of the wheel, as for example, the armature shaft of an electrical genera-tor driven from the wheel axle. It will be understood that the driving connection to the pulley I8! on the shaft 81 is such as not to permit any slippage of the pulley IGI relative to the vehicle wheel except possibly under extraordinary circumstances to prevent breakage of mechanical parts due to unusual mechanical stresses.

The fiy-wheel 86 is rotated by rotation of the shaft 8? through a clutch arrangement comprising a disc I03 fixed to the shaft, and a coil spring I04 so interposed between a collar or flange I05 fixed to the shaft 3? within the hub portion 93 of the fly-wheel and an annular shoulder I06 within the bore 92 of the hub portion 93 of the fly-wheel, as to urge the fly-wheel 86 and the disc I03 into interlocking or clutching engagement. Suitable thrust bearings It! are provided for sustaining the axial thrust of the pulley IOI on the end cover 9| due to the force of the spring I04 and also the thrust of the spring I04, on the fiywheel 86, so as to minimize the frictional forces resisting rotation of the shaft and the flywheel 86.

The disc I03 and fly-wheel 86 are interlocked by means of a plurality of spaced pairs of complementary registering recesses I09 and H0 in the juxtaposed faces of the disc and fly-wheel, in each of which pair of complementary recesses is contained a steel ball II I. Any suitable number of pairs of recesses I 39 and H0 may be provided arranged in spaced circumferential relation at a given radial distance from the axis of the shaft 81. The recesses I09 and H0 are relatively short and have a substantially constant radius of curvature about the axis of the shaft 87 so that the recesses resemble somewhat the contour of a kidney bean.

Each of the recesses I 09 and I I 0 varies in depth along the arc thereof with respect to the face of the disc or fly-wheel in which they are located, being deepest at the mid-point and sloping upwardly in opposite directions to the face of the disc or fly-wheel.

It will thus be seen that under the influence of the spring I04, the steel balls III normally seat in the deepest portion of each pair of complementary recesses led and H0 so that the flywheel 86 and the disc I03 are accordingly normally interlocked for rotation together.

The compressive force or strength of the spring (III I04 is such as to maintain the fly-wheel 86 and disc I03 in interlockingengagement, as shown, as long as either the disc or the fly-wheel does not accelerate or decelerate with respect to each other in excess of a certain rate corresponding, for example, to a ten mile per hour per second rate of retardation or acceleration of the vehicle wheel driving the shaft 81. Such a high rate of acceleration or deceleration of the vehicle wheel will not occur except by exceeding the limit of adhesion between the vehicle wheel and the rail surface along which the wheel rolls, that is, by slipping the wheel. Thus, when a vehicle wheel and the shaft 81 driven by the wheel are rotatively decelerated at a rate in excess of ten miles per hour per second when the wheel begins to slip, and subsequently accelerated at a rate in excess of ten miles per hour per second when the vehicle wheel accelerates back toward a speed corresponding to vehicle speed while slipping, the fly-wheel 36 shifts rotatively forward and then backward, relative to the disc I03. That is, when the shaft 81 decelerates at a rate corresponding to the deceleration of the vehicle wheel while slipping, the fiy-wheel 86 tends to over-run, that is, rotate faster than or lead the shaft 81 and, when the shaft 81 accelerates according to the rate of acceleration of the vehicle wheel back toward a speed corresponding to vehicle speed while slipping, the fly-wheel 86 tends to lag behind or rotate slower than the shaft 81.

In view of the steel balls III interposed between the disc I03 and the fiy-wheel 86, the rotative shift of the fly-wheel 86 relative to the disc, either forwardly or backwardly of its normal position, causes the fly-wheel 86 to be shifted axially in the right-hand direction against the yielding resisting force of spring I04.

. The degree of rotative shift of the fly-wheel 86 relative to the disc I03 is limited to a degree which prevents the steel balls leaving the complementary recesses I09 and H0, as by one or more pins (not shown) in the disc or fly-wheel cooperating with arcuate slots or grooves (not shown) in thefly-wheel or disc, in the manner shown and described in my above-mentioned copending application.

The switch device 88 of the wheel-slip responsive device 2| comprises a pair of cooperating resilient. .contact fingers H5 and H6, each of which is fixed at one end to an insulating member II'I secured within the casing 85 at the end of the hub portion 93 of the fly-wheel. The contact fingers H5 and HG are disposed in spaced parallel relation so that the free ends of the contact fingers are normally disengaged. When the fly-wheel 85 is shifted in the right-hand direction, as a. result of shifting rotatively relative to the disc I03, the end of the hub portion 93 of the fly-wheel engages the free end of a resilient spring member I I8 which is fixed at the opposite end in the insulating member Ill and bends it laterally against the contact finger I I5 to shift it into contact with the contact finger H6. A tip II9 of insulating material is provided on the spring member H0 for engaging the contact finger H5, thus preventing the grounding of the contact finger II5 to the casing 85.

It will thus be understood that the wheel-slip responsive device 2I is representative of any suitable device for closing an electrical circuit substantially instantaneously upon the slipping of a vehicle wheel.

' The pressure-operated switch 22 is diagrammatically shown as comprising a casing having a piston I2I for operating a movable switch member I22 into and out of contact with a pair of stationary spaced contact members I23 suitably carried in insulated relation on the casing. .As

ton I2I opposite to the spring I25 is a chamber I23 which is constantly connected to that portion of the straight-air pipe I5 between the brake valve I3 and the release valve IS. The strength of the spring I25 is such that when the fluid pressure established in the straight-air pipe I5 and effective in chamber I26 on the piston I2I exceeds a relatively low pressure, such as two or three pounds per square inch, the resisting force of the spring I25 is overcome and the piston I2I is shifted upwardly to effect contact of the switch member I22 with the contact members I23 in circuit-closing relation. 7

One of the stationary contact members I23 of the pressure-operated switch 22 is connected by a wire I3I to one terminal, such as the positive terminal, of battery 23 and the other contact member I23 is connected by a wire I32 to one terminal of the electromagnet winding of the magnet valve I I as well as to the-contact finger H5 of the wheel-slip responsive device 2| by a branch wire I33 of the wire I32. Contact finger IIS of the wheel-slip responsive device 2I is connected by a wire I3 to one'terminal of the electromagnet winding I5 of the magnet valve I9 and the other terminal of the electromagnet winding I5 is connected to the negative terminal of the battery 23, as through a ground connection in the manner shown.

The terminal of the electromagnet winding 45 of the magnet valve II opposite to that connected to the contact member I23 of the switch 22 is connectedby a wire I35 to one of the contact members 62 of the pressure-operatedswitch I8 and the other contact member 62 of the switch I8 is connected to the negative terminal of the battery 23, as through a ground connection in the manner shown.

It will thus be seen that with the pressure switch 22 and the switch 88 of the wheel-slip responsive device 2I both closed, a circuit is established for energizing the electromagnet winding I5 of the magnet valve I9. It will also be seen that with the pressure switches I8 and 22 both in circuit-closing position, a circuit is established for energizing the electromagnet winding 45 of the magnet valve II.

Operation of embodiment shown m-Fig. 1

Let it be assumed that the main reservoir I2 is charged to the normal pressure carried therein, as by a fluid compressor (not shown), that the car or train is traveling along the road under power and that it is desired to effect an application of the brakes. After first cutting off the propulsion power of the car or train, the operator shifts the brake valve handle 25 into the application zone an amount corresponding to a desired degree of application of the brakes. Fluid under pressure is accordingly supplied through the straight-air pipe I5 to the brake cylinder II and the pressure established in the straight-air pipe and the brake cylinder corresponds to the de gree of displacement of the brake valve handle out of its normal release position.

As previously stated, the release valve it remains in the position shown to establish communication between the two portions of the straight-air pipe l5 and is not actuated out of such position except under circumstances hereinafter to be described.

Let it now be further assumed that the application of the brakes efiected in the manner just described causes a vehicle wheel with which the brake cylinder H is associated to begin to slip. In such case the wheel-slip responsive device 2! is operated to close the switch device 83 thereof and accordingly establish the circuit for energizing the electromagnet winding 15 of the magnet valve l9, it being understood that the pressure switch 22 is in circuit-closing position due to the pressure established in the straightair pipe l5. Magnet valve l9 operates in response to the energization of the electromagnet winding 15 thereof to cause fluid under pressure to be supplied from the straight-air pipe l5 and brake cylinder H to the chamber 64 of the pressure-operated switch l8, which is accordingly actuated to circuit-closing position to effect energization of the electromagnet winding of the magnet valve ll.

Magnet valve ll accordingly operates in response to the energization of the electromagnet winding 45 thereof to rapidly vent fluid under pressure from the piston chamber 32 of the release valve device IB, which in turn operates in response to such reduction of pressure in the chamber 32 to interrupt the supply communication through the straight-air pipe I 5 and vent fluid under pressure from the brake cylinder H at a rapid rate through the exhaust port 36. It will be understood that in practice the release valve I6 is located close to the brake cylinder H to aid in effecting the rapid reduction of the pressure in the brake cylinder II.

As previously explained, when fluid under pressure is once supplied to the piston chamber 64 of the pressure switch N3, the valve 56 is unseated and consequently direct communication is established between the chamber 64 and straightair pipe 15 independently of the magnet valve Hi. It will thus be seen that, independently of the rotative condition of the vehicle wheel and therefore of the wheel-slip responsive device 2|, pressure switch i8 is maintained in circuit-closing position once it is shifted to circuit-closing position and remains in that position as long as the pressure in the brake cylinder 1 I and the connected portion of the straight-air pipe l5 contains fluid at a pressure in excess of the five pounds per square inch pressure necessary to hold the contact member in engagement with the contact members 62.

As previously pointedout, as long as the chamber 32 of the release valve I6 is connected to atmosphere, the piston valve 21 thereof is maintained in its raised or venting position. Therefore, it will be seen that since the pressure switch I8 is maintained in circuit-closing position as long as the brake cylinder pressure exceeds the low pressure of five pounds per square inch, the release valve I6 is also correspondingly maintained in venting position as long as the pressure in the brake cylinder exceeds the low pressure of live pounds per square inch. Consequently, the reduction of the pressure in the brake cylinder II to below five pounds per square inch is positively guaranteed, once the wheel-slip responsive device 2| operates in response to the'initiation of slipping of the vehicle wheel to close the switch 88 thereof, independently of the subsequent opening of switch 88.

Due to the rapid reduction of pressure in the brake cylinder H and the consequent rapid release of the brakes on the wheel which begins to slip, the slipping wheel ceases decelerating and begins to accelerate back toward a speed corresponding to vehicle speed while the pressure in the brake cylinder is still considerably in excess of the predetermined low pressure required to maintain pressure switch l8 in circuit-closing position. It will accordingly be seen that the fly-wheel 86 of the wheel-slip responsive device 22 shifts from a leading to a lagging rotative position with respect to the disc (03 on the shaft 87 when the vehicle wheel changes from decel-' eration to acceleration. Momentarily, therefore, the fly-w'heel 8B is shifted axially back to its normal position in a left-hand direction sufficiently t0 eifect disengagement of the contact fingers H5 and I I6 of the switch device 88 before returning in the right-hand direction again to eifect reengagement of the contact fingers H5 and H6.

The electromagnet winding 15 of magnet valve i9 is thus momentarily deenergized but such momentary deenergization is ineffective to cause operation of the pressure switch 18 correspondingly to circuit-opening position because the pressure of the brake cylinder is still effective to maintain the switch H3 in circuit-closing position. It will be seen that the momentary decnergization of the electromagnet winding 15 of the magnet valve l '9 due to the change in rotative condition of the vehicle wheel from deceleration to acceleration does not cause operation of the piston valve '21 of the release valve Hi from its venting position. Accordingly, once the vehicle wheel begins to slip, the reduction of brake cylinder pressure to below the certain uniform low pressure of five pounds'per square inch is guaranteed independently of variation in the rotative condition of the vehicle wheel.

In view of the fact that the acceleration of a slipping wheel back toward a speed corresponding to vehicle speed is at a high rate, the slipping wheel will, under average conditions of adhesion between the wheel and rail, attain a speed corresponding to vehicle speed before the brake cylinder pressure reduces to the certain uniform low pressure of five pounds per square inch required to maintain pressure switch l8 in circuitclosing position.

When the pressure in the brake cylinder ll reduces suificicntly to enable the spring 6| of the pressure switch 18 to effect operation of the switch member 55 to circuit-opening position, the electromagnet winding es of the magnet valve 5'? is deenergized and consequently the exhaust communication for the piston chamber 32 of the release valve I6 is closed.

The restricted port 38 in the operating piston 28 of the application valve H3 is of sufiicient size that, when the exhaust communication of the piston chamber 32 is closed, the pressure in the piston chamber 32 is rapidly built up to the pressure established in the chamber 31 on the opposite side of the piston communicating with the straight-air pipe l5. As a result, the piston valve 21 is shifted promptly downward to close the exhaust port 36 and reestablish the supply communication between the two portions of the straight-air pipe l5 when the pressure in the brake cylinder ll reduces below the predetermined uniform low value of five pounds per square inch.

It will be noted that such supply communication is not reestablished by the release valve it until after the wheel which slipped has attained a speed corresponding to vehicle speed \and, therefore, that the contact fingers H and N6 of switch device 88 of the wheel-slip responsive device 2| will have separated by the time that the piston valve 21 of the release valve 16 is returned to a position closing the exhaust port 36 and reestablishing communication between two portions of the straight-air pipe I5. In such case, therefore, with the valve 12 of the magnet valve l9 seated due to the denergization of the electromagnet 75, the resupply of fluid under pressure through the straight-air pipe to the brake cylinder II will not result in a subsequent operation of the pressure switch l8.

It will be evident that when the vented portion of the straight-air pipe I5 between the release valve 56 and the brake cylinder is reconnected to the portion of the straight-air pipe l5 which remains charged, the pressure of the fluid in the charged portion of the straight-air pipe reduces due to the flow of fluid under pressure from that portion to the uncharged portion and to the brake.

cylinder H.

As previously explained, the self-lapping brake valve l3 operates automatically to maintain the pressure in the straight-air pipe l5 proportionate to the degree of displacement of the brake valve handle out of its normal position. Thus, when the pressure in the charged portion of' the straight-air pipe l5 reduces, the brake valve l3 operates automatically to supply fluid under pressure into the straight-air pipe to restore a pressure therein and in the brake cylinder I i corre- 'sponding to the degree of displacement of the brake valve handle out of its normal position.

As previously pointed out, the brake control apparatus constituting my present invention is adapted to be employed in connection with modern high speed train equipment in which a speed governor or retardation controller automatically operates to reduce the degree ofapplication of the brakes on the train as the speed of the train reduces. Thus even though the brake valve handle 25 remains in the application position to which it was originally shifted, the actual pressure restored in the brake cylinder may be less than that which initiated the slipping or' the vehicle wheels. Furthermore, even with or without such automatic devices the engineer of a train customarily reduces the degree of application of the brakes, as the speed of the car or train reduces, in order tocompensate for the increase in the coefiicient of friction between the brake shoes and wheels which takes place.

Accordingly, due either to the automatic operation of the speed governor or retardation controller-device, or to the manual operation. of the brake valve I3, the degree of pressure restored in the brake cylinder following the return of 'the slipping wheel to a speed corresponding to vehicle speed may be less than that which initiated the slipping of the wheel. Consequently, recurrence of slipping of the vehicle wheel is unlikely. However, if upon reapplication of the brakes the pressure in the brake cylinder associated with a slipping wheel again causes the wheel to slip, the brake control equipment will again function to vent fluid under pressure from the brake cylinder and subsequently resupply fluid under pre'ssurethereto. In any case, the

equipment constituting my invention definitely and positively prevents sliding of the vehicle the degree of application of the brakesis not reduced rapidly enough, due for example to friction in the brake rigging, it may happen that the vehicle wheel will decelerate to a relatively low speed before beginning to accelerate back toward a speed corresponding to vehicle speed. In such case, the switch device I8 may be operated to circuit-opening position in response to the sufficient reduction of the pressure in the brake cylinder, while the vehicle wheel is still accelerating at a suificient rate to effect closing of the switch 88 of the wheel-slip responsive device 21. The electromagnet 15 of the magnet valve device l9 will thus be energized and fluid under pressure will be supplied to the chamber 6% of the pressure switch l8 from straight-air pipe I5 when the release valve I6 is operated to re-.

store communication through the straight-air pipe in response to opening of the switch device i8. Thus switch device l8 will be operated instantly again to circuit-closing position and release valve it will be instantly operated to again vent fluid under pressure from the brake cylinder. Accordingly, it will be seen that in no case is pressure substantially in excess of the relatively ..1

low uniform value of five pounds per square inch permitted to be resupplied to the brake cylinder before the slipping wheel returns substantially to a speed corresponding to vehicle,

In the case of conventional clasp type wheel,

brakes employed on present day railway cars, it is well knownthat the fluid pressure in the op-- erating brake cylinder must exceed five pounds per square inch before the brake shoes begin to exert a retarding force on the vehicle Wheel. Thus, under the conditionsjust mentioned, even though fluid under pressure may be resupplied to the brake cylinder up to a pressure of five pounds per square inch, the brakes will not operate to exert a retarding force on the vehicle Wheel because the pressure switch 3 does not permit the pressure to exceed five pounds per square inch as long as the switch 88 of the wheel-slip responsive device is closed.

Assuming that the car or train of cars has been brought to a stop due to application oflthe, brakes and that the operatordesires to release the brakes prior to again starting the car or train, this may be efiected by returning the brake valve handle 25 to its release position. Fluidunder pressure is as aresult vented fromthe brake cylinder through the straight-air pipe under the control of the brakewvalve and the brakes are thus completely released.

In the event that the wheels of the traction car or locomotive race due to the application of propulsion power thereto, switch 88 of the wheelnet valve device I9 and operation of release valve it is accordingly prevented.

Modified arrangement shown in Fig. 2

Referring to Fig. 2, a modified arrangement of the apparatus shown in Fig. 1 is disclosed wherein the fluid under pressure supplied to the chamber s of the pressure switch l8 under the control of the magnet valve 19 is from an independent source, such as a reservoir I38, instead of the straight-air pipe l5 and brake cylinder 1 i as in Fig. l. Reservoir I38 may be charged in any suitable manner as from a train pipe, not shown, connected to the main reservoir 12. The operation of modified arrangement shown in Fig. 2 is otherwise same as described for that of the equipment shown in Fig. 1 and is accordingly not repeated.

Embodiment shown in 3 switch are designated by the same reference numerals. Valve device 55A diiiers from pressure switch It! in that the stem 53 of the operating piston Fl -t is effective, when the piston 54 is shifted upwardly, to-unseat a valve iii! of the poppet type instead of operating the switch member The casing of the valve device 58A. suitably formed to provide a cl'iamber H52 in which the valve 852 is contained and which is constantly connected to the piston chamber 32 of the release valve I6 through the connecting pipe ll. interposed between the valve l5! and a cap screw $53 screwed into the outer open end of the chain.

her is a coil spring E 54 which yieldingly urges the valve ifil into seated relation on an associsted valve seat. The valve ltll has a fluted stem 155 which extends slidably through a suitable bore in the casing into a chamber i555 which is constantly open to atmosphere through port I51, the end of the fluted stem E55 being adapted to be engaged by the end of the stem 5d of the piston The upward movement of the operating piston 55 from its normal position shown is limited by the engagement of the piston 5 with downwardly extending boss 8% formed in the casing and extending downwardly into the chamber 58 so that the port 59 is not lapped or closed and so that the degree to which the valve [5| i unseated from the valve seat is correspondingly limited.

As in the equipment shown in Fig. 1, magnet valve i9 is arranged to cause fluid under pressure to be supplied from the straight-air pipe 55 and brake cylinder H to the chamber 5 8 beneath the operating piston M of the valve device [8A.

It will thus be understood that when the magnet valve device i3 is energized by current supplied over the wire i3 3 under the control of switch 238 of the wheel-slip responsive device 2i, fluid under pressure is supplied to the chamber 6 to cause the operating piston 5a to be shifted upwardly to its upper limit position. Thus the valves lei and 56 are simultaneously. unseated, the valve 58 establishing direct communication from the straight-air pipe i5 and brake cylinder l i, to the chamber 64 of the valve device WA and the valve l5! establishing an exhaust communication from the piston chamber of the release valve device l5 to atmosphere through port I57.

When the pressure in the straight-air pipe l5 and brake cylinder H reduces sufficiently, the spring 55 shifts the piston fi l downwardly to effect reseating of the valves 56 and lfii. The reseating of the valve l5! isolates the piston chamber 32 of the release valve iii and consequently the release valve 26 is operated to restore the supply communication to the brake cylinder, as in the equipment shown in Fig. l.

The above description of the embodiment shown in Fig. 3 is believed suificient when taken with the above description of theoperation of the equipment shown in Fig. 1 so that an understanding oi the complete operation of the embodiment shown in Fig. 3 may be had without further description.

Embodiment shown in 4 In Fig. l. another embodiment of my invention is shown which difiers from that shown in 3 in omitting the magnet valve device l9 and in providing an electropneumatic valve device lBB in place of the pressure operated valve device 18A.

The electropneumatic valve device l8B is similar in part to the pressure operated valve device HM. and accordingly parts of the valve device lilB which correspond to those of the pressure operated valve device USA are not described but are indicated by identical reference numerals. sentially, the electropneumatic valve device |3B differs from the pressure operated valve device NBA in the addition of a solenoid or electromagnet winding E65 arranged so that, when it is energized, it magnetically actuates an associated plunger H52 upwardly to unseat the valve I61 and also to shift the piston 5 upwardly to effect unseating of the valve 5%. As will be apparent from the drawings, the plunger N52 is screwed to the upper end of the stem 58 of the operating piston 5t and the upper reduced end of the plunger is guided in a suitable bushing I53 fixed in the casing, the upper end of the plunger extending into the chamber I56 and being adapted to engage the lower end of the fluted stem I55 of the valve lfii.

The electromagnet winding I6! is arranged to be energized and deenergized under the control of the switch device 88 of the wheel-slip device 2i in exactly the same manner as is the electro magnet winding it of the magnet valve device iii of previous embodiments. This is indicated by the fact that the one terminal of the electromagnet winding I5! isconnected to the negative terminal of the battery 23 through a ground connection, in the manner indicated, and the other terminal is connected by the wire I34 to the contact finger N6 of the switch device 88 of the wheel-slip responsive device 2!. 1

In operation, when the electromagnet winding it! is energized, the plunger I62 is actuated upwardly by the magnetic force exerted thereon and consequently the valve l5l and 56 are simultaneously unseated to effect the same result as in the embodiment shown in Fig. 3. Since the valve 55 when unseated establishes a direct communicaion between the straight-air pipe l5 and the pressure chamber 64 of the electropneumatic valve device lBB, it will be seen that the valve l5! will be maintained unseated as long as the pressure in the straight-air pipe i5 and brake cylinder H exceeds the certain uniform low presxiii,

sure of five pounds per square inch, notwith-.-

standing deenergization of the electromagnet winding I6I.

It is believed that the above description of the embodiment shown in Fig. 4 taken with the description of the operation of the embodiment shown in Fig. 1 will'be suflicient to give a complete understanding as to the operation of the embodiment shown in Fig. 4 without further detailed description.

Embodiment shown, in. Fig. 5

In Fig. 5, is shown the preferred embodiment of my invention. This embodiment differs from the embodiment shown in Fig. 4, by the inclusion of a reapplication control valve device I1I for controlling the rate of resupply of fluid under pressure to the brake cylinder following relief of a wheel slipping condition. I

This embodiment comprises in part the release valve I6 and the electropneumatic valve device I8B already described in the embodiment of Fig. 4 and accordingly the various elementsof these devices shown in Fig. 5 are designated by corresponding reference numerals.

The reapplication control valve device I1I comprises a sectionalized casing having a. valve section I12, a cover or end section I13 for the valve section I12, a piston section, I14 and an end or check-valve section I15 for the piston section I14, all of the various casing sections being secured together in sealed relation, in the manner shown, by suitable bolts or screws not indicated.

. The valve section of the casing I12 is provided with a bore I18 in which operates a piston valve I19. The piston valve I19 has inset therein at one end an annular gasket I8I which is adapted to seat on an annular rib seat I82 formed on the piston section I14 of the casing and extending into the open end of the bore I18. At the opposite end of the piston valve I19 is a stem I83 having a flange or collar I84 fixed thereto. A coil spring I85 is interposed between the collar I84 on the stem I83 and a shoulder formed at the end of the bore I18 for yieldingly urging the piston valve I19 in the right-hand direction into seated relation on the annular rib seat I82.

The piston valve I19 is arranged to control communication through that section of the straight-air pipe I5 which connects the brake valve I3 and the annular chamber 31 of the release valve I6. To this end, the portion of the straight-air pipe I5 just. referred to is divided into two sections, that section connected to the brake valve I3 opening into the bore I19 at one point and that section of the straight-air pipe connected to the release valve I6 opening into the bore I18 at another point circumferentially spaced from but in alignment with the opening of the other section connected to the brake valve.

When the piston valve I19 is urged into seated relation on the annular rib seat I82, the opening of the two sections of the straight-air pipe I5 just referred to into the bore I18 are uncovered and consequently fluid under pressure may be supplied through the straight-air pipe I5 at a rapid rate under the control of the brake valve I3.

When the piston valve I19 is shifted in the left-hand direction in the manner presently to be described and thus unseated from the annular rib seat I82, the opening of the two sections of the straight-air pipe I5 .into the bore I18 are lapped or covered and thus the supply of fluid under pressure through the straight-air pipe I5 under the control of the brake valve I3 is cut.

off except for a by-pass communication formed by a passage I81 around the piston valve I 19 I which extends through the cover section I13 of the casing. A choke element I88 having a restricted passage I89 therein is suitably secured to the cover section I13 within the passage I81 and serves to restrict the rate of supply of fluid under pressure through the straight-air pipe I5 under the control of the brake valve to a relatively slow rate, when the piston valve I19 is shifted in the left-hand direction to lap the openings of the two sections of the straight-air pipe I5 into the bore I18. p

The passage I81 is connected through a short passage I9I into the bore I18 so that the pressure of the fluid supplied through the choke element I88 is effective on the left-hand face of the piston valve I19 to assist springl85 in returning the piston valve I19 in the right-hand direction into seated relation on the annular rib seat I82.

The piston section I14 of the casing has a bore I93 in which operates a piston I94which is relatively large in area compared to the cross-sectional area of piston valve I19. Piston I94 is provided with a suitable sealing ring I95 for engaging the surface of the casing within the bore I93 and is further provided with an axial stem I96 which extends slidably through a suitable opening I91 in the end wall of the-casing section I14 into the bore I18 of the casing section I12 at a point within the annular rib seat I82. Thus, when the piston I94 is shifted in the left-hand. direction from the position shown, the end of the stem I96 engages the end of the piston valve I19 at a point within the annular gasket IBI and shifts the valve in the left-hand direction against the yielding resisting force of the spring I85 and. fluid pressure acting on the left-hand face of the piston valve if the straight-air pipe I 5 is charged with fluid under pressure.

Inset in the face of the piston at the base of the stem I96 is an annular gasket I98 which is adapted to seat on an annular rib seat I99, formed on the end wall of the casing section I14 in surrounding relation to the stem .196, when the piston I94 is shifted sufficiently far in the left-hand direction.

Formed between the piston I94 and the end wallof the casing I14, that is at the left of the piston, is a chamber 2III which is constantly open to atmosphere through an exhaust port 292.

The gasket I98 is effective when seated on the annular rib seat I99 to prevent the leakage of fluid under pressure from the straight-air pipe I5 past the piston valve I19 and along the stem I96 through the bore I91 to the atmospheric chamber 20I. The gasket I8I on piston valve- I19 is effective when seated on the annular rib seat I82 to serve the same purpose.

Formed between the piston I94 and the end section I15 of the casing is a chamber 294 to which fluid under pressure is supplied and from which fluid under pressure is released under the.

control of the electropneumatic valve device I83 in the manner to be hereinafter explained. Centrally formed on or attached to the inner face of the end section I15 of the casing is a stem 205 which projects into the chamber 264 and serves as a stop to limit the movement of the piston I94 in the right-hand direction to an amount just suflicient to permit seating of the piston valve I19 on the annular rib seat I82.

Due to the fact that piston I94 is larger in area than the piston valve I19 and also to the fact that the major portion of the left-hand face pressure when the piston I94 seats on the an-- nular rib seat I99, it will be seen" that a relatively low fluid pressure acting on piston I94 in chamber 294 may be effective to holdpiston valve I19 displaced in a position to lap the openings of the straight-air pipe into bore I18 against a relatively high fluid pressure acting through passage I9I on the left-hand face of the piston valve.

Formed in the endsection I15 of the casing is a passage 281 which opens at the outer face of the casing section 115 and has two branches 288' and 299 each of which opens at the inner face of the casing section into the chamber 284. Contained in the branch 288 of the passage 291 is a one-way or check valve 211, illustrated as of the ball type, the check valve 2II being so arranged as to permit a rapid supply of fluid under pressure therepast into the chamber 294 and to prevent :reverse flow of fluid under pressure therepast. Suitably secured to the casing section I15 within the branch 299 of the passage 281' is a choke element 2I2 having a restricted passage 2I 3 therein. The choke element ZI-Z serves to restrict the rate at which fluid under pressure may be vented from the chamber 28-9 thereby serving a purpose which will be made apparent hereinafter.

The passage 281 of the reapplication control valve device I is connected by a pipe 2I5 to a passage and port 2I6 which opens into the atmospheric chamber 58 of the electropneumatic valve device IBB at a point just above the piswinding IBI (see Fig. 4), the piston 54 shifts to a point above the port 216 and accordingly the fluid under pressure in the brake cylinder H and straight-air pipe I5'flows at a rapid rate through the pipe 2I5 and past the check valve 2H" into the chamber 294.

It will be understood that, as inthe embo.d1--

ment shown in Fig. 4, the electromagnet winding I6I of the electropneumatic valve device I8B is energized and deenergized under the control of the switch device 88 of the wheel-slip responsive device ZI, this being indicated by the fact that vthe wire connected to one terminal of the-electromagnet winding is designated as the wire I34 which, as indicated in Fig. 1-, is connected to the contact finger H5 of the switch device 88-.

Operation of embodiment shown in Fig. 5

Let it be assumed that an application of the brakes has been effected by operation of the brake valve I3 (see Fig. 1) and that the straightair pipe I5 and brake cylinder I I are thus charged with fluid at a presseure corresponding to the degree of displacement of the brake valve handle 35 out of release position. Let it be further assumed that while the brakes are applied as just described, a vehicle wheel on which the brakes upwardly to effect unseating of the valves 56 and- I5I-, as described for the embodiment shown in Fig, 4. The release valve I8 is instantly operated to close the supply communication through the straight-air pipe I5 and to vent fluid under pressure from the brake cylinder II. Furthermore, the unseating of the valve 59 subjects the piston 54 of the valve device I'8B- to the pressure in the brake cylinder to maintain the valves 55 and I5I in unseated position as long as the pressure in the brake cylinder exceeds a certain uniform low pressure of for example five pounds per square inch.

In shifting to its upper position, the piston 54- of the valve device I8B connects the port 218 to the chamber 5 1 beneath the piston 54 and thus fluid under pressure is supplied from the brake cylinder II by way of chamber 94-, pipe.

2I5 and past the check valve 2 into the chamber 28 1' of the reapplication control valve device I1I. It will be seen that the rate of reduction of brake cylinder pressure efiected in response to slipping of the vehicle wheel in the embodiment shown in Fig. 5 is somewhat faster than the rate of reduction in brake cylinder pressure of the previous embodiments, due to the exhaust of fluid under pressure to the chamber 294 of the reapplication control valve device I'II in addition to the exhaust through port 36 of release valve I6.

The chamber 28 lof the reapplication control valve device I1I is rapidly charged to a pressure somewhat below the original pressure established in the brake cylinder I I. This pressure is effective to exert a force on the piston I94 to shift it into seated relation on annular rib seat I99 and to shift the piston valve I19 in the lefthand direction to close the connection through bore I18 between the two sections of the straight-.

air pipe I5 against the combined opposing force of the spring I85'and the pressure established in the straight-air pipe I5- acting on the left-hand face of the piston valve I19 in the bore I18. It will thus be apparent that as long as the piston valve I19 is in the position just described, the supply of fluid under pressure through the straight-air pipe I5 will be limited to the restricted rate determined by the restricted passage I89 of the choke element I88 in the by-pass communication around the piston valve I19 through the passage I81. the restricted passage I89 is of larger flow area than the restricted passage 38 in operating piston 28 of the release valve I5 so as to permit the supply of fluid under pressure through the straight-air pipe I5 to the chamber 81 of the release valve device IE to maintain sufl'icient upward force on the operating piston 28 to keep the piston valve 21 in its raised position in which fluid under pressure is vented from the brake cylinder II.

As in the operation of the embodiment shown in Fig. 1, when the slipping wheel ceases deceleration due to the reduction of brake cylinder pressure and begins to accelerate back toward a speed corresponding to vehicle speed, the electromagnet winding I6I- of the valve device I8B is momentarily deenergized due to the momentary opening of the switch 88 of wheel-slip responsive device 2 I. However, as in the case of the pressure switch I8 of the embodiment shown in Fig. 1, such momentary opening of the switch 88 is without effect because the brake cylinder pressure acting in the chamber 64 beneath the operating, piston 54 of the valve device I8B maintains the piston It should be understood thatnormal position by the spring 61.

As stated in the operation of the equipment shown in Fig. 1, the slipping vehicle wheel accelerates rapidly back toward and attains a speed corresponding to vehicle speed before the pressure in the brake cylinder II and chamber 64 of the valve device I8B is reduced sufficiently to permit the return of the piston 54 downwardly to its Thus after the slipping vehicle wheel has returned fully to a speed corresponding to vehicle speed, the piston 54 is returned downwardly to effect seating of the valves 56 and II. The reseating of the valve I5I causes the release valve I6 to be operated promptly to restore the supply communication through the straight-air pipe I5 to brake cylinder II while the reseating of valve 56 closes communication from brake cylinder II to chamber 64 of valve device I8B.

ciently that the fluid pressure remaining in the chamber 204 after the piston 54 of the valve device I8B is returned downwardly to its normal position maintains the piston I94 seated on the annular rib seat I99. Thus notwithstanding the return of the release valve I5 to its normal position restoring the supply communication through the straight-air pipe I5 to the brake cylinder II, the rate of restoration of pressure in the straightair pipe and in the brake cylinder II is determined by the rate of supply of fluid under pressure through the restricted passage I89 of the choke element I88 in the reapplication control valve device I1I.

It will be seen that after the operating piston 54 of the valve device I8B is returned downwardly to a position in which the valve 55 is seated, the fluid remaining in the chamber 204 of the reapplication control valve device I1I continues to be vented to atmosphere through the choke element 212 and exhaust port 59 above the piston 54.

The flow area of the restricted passage 2I3 of the choke element 2 I 2 may be so selected in relation to the volume of the chamber 204 that the force exerted by the fluid pressure in the chamber 204 on the piston I94 will be reduced sufficiently to permit the return of the piston valve I19 in a right-hand direction into seated relation on the annular rib seat I82 while the car ortrain of cars is approaching a stop and before it is actually completely stopped, or it may be so selected that the pressure in chamber 204 is not suiflciently reduced to permit return of piston valve I19 to its normal position until after the car or train has been brought to a complete stop. In any case, when the piston valve I19 reopens the communication through the bore I18 connecting the two sections of the straight air pipe I5, it reestablishes communication through the straightair pipe I5 whereby fluid under pressure may be rapidly resupplied to the brake cylinder II, unless the pressure in the straight-air pipe I5 and brake cylinder II has been built up to its maximum restored value prior thereto.

As described in the case of the embodiment shown in Fig. 1, soalso it must be understood that the equipment shown in Fig. 5 is in practice employed in a high speed train brake equipment having a speed governor or a retardation controller for automatically reducing brake cylinder pressure as the speed of the car or train reduces under an application of the brakes.

Thus, due either to the automatic reduction in brake cylinder pressure or to operation of the brake valve I3 to reduce the pressure in the straight-air pipe I5, as in the case of the equipment shown in Fig. 1, the ultimate pressure restored in the brake cylinder may be less than that which initiated the slipping of the vehicle wheels so that the possibility of recurrence of slipping of the vehicle wheels is minimized.

It will be apparent also that in the case of the equipment shown in Fig. 5, the restriction of the rate of resupply offluid under pressure to the brake cylinder, following slipping of the vehicle wheel, also tends to minimize the likelihood of recurrence of wheel slipping, because reapplication of the brakes to an appreciable degree is not effected before a slipping wheel returns fully to a speed corresponding to vehicle speed.

The restriction of the resupply of fluid under pressure to the brake. cylinder associated with a vehicle wheel which has slipped is also effective to prevent undesirable slack action in a train of cars. It will be apparent that, if the brakes associated with the wheel and axle units ondifierent cars-are suddenly released and then suddenly reapplied under the control of wheel slipping means associated with the wheels on the different cars of the train, the slack between successive cars may run in or out with some degree of severity. Thus, by restricting the rate of resupply to the brake cylinder the possibility of severe running in or running out of slack between cars is minimized.

In the case of certain types of high speed trains having a relatively few number of cars of the so-called articulated type, the problem of slack action will of course not arise, but the sudden reapplication and sudden release of the brakes on wheel and axleunits of difierent cars may result in an undesirable jerking or bucking of the cars causing discomfort to passengers. The slow rate of reapplication however tends to minimize this undesirable bucking action and cause smooth braking action.

Since the piston valve I19 of the reapplication control valve device IN is automatically restored to its normal position as previously described, the brakes may be rapidly'released when it is desired to again start the car or train after it has been brought to a stop, by operating the brake valve handle 25 to release position. In such case, fluid under pressure is vented from the brake cylinder through the straight-air pipe I5 to atmosphere at the brake valve I3, complete release of the brakes being thereby efiected.

It will be understood that the pressure switch 22 shown in Fig. 1 is also a part of the equipment of the embodiment shown in Fig. 5 although it is not shown in Fig. 5. As in the case of the equipment shown in Fig. 1, the pressure switch 22 is effective to prevent undesired completion of the electrical circuits and consequent energization of electroresponsive devices operative on such circuits when the switch 88 of the wheel-slip responsive device 2I is closed .due to racing of the wheels of the traction car or'locomanually controlled means motive of' the train caused by the application of propulsion power to the car or train.

Summary Summarizing, it will be seen that I have disclosed various embodiments of my invention, all of which embody a common principle, namely the prevention by means under the control of brake cylinder pressure of the reapplication of the brakes on a slipping wheel until after the slipping Wheel has returned to a speed corre-' ,wheel to a certain uniform low pressure notwithstanding variation in the rotative condition of the vehicle wheel eifected in response to the reduction of brake cylinder pressure. Thus the slipping vehicle wheel may return to a speed corresponding to vehicle speed before reapplication of the brakes on the slipping wheel will be eifected.

In the preferred embodiment of my invention shown in Fig. 5, a reapplication control valve device is provided which is operated by fluid under pressure vented from the brake cylinder, in response to the slipping of a vehicle wheel, to a position for restricting the rate of resupply of fluid under pressure to the brake cylinder which is effected automatically after the pressure in the brake cylinder has reduced to the certain uniform low pressure determined by the pressure responsive device.

While I have illustrated my invention in simple diagrammatic form in connection with only -one brake cylinder, the manner of adaptation and application thereof to a brake control equipment for a train of cars Will be readily apparent,

as will other additions or modifications, without departing from the spirit of my invention. It is' accordingly not my intention to limit the scope of my invention except as it is necessitated by the scope of the prior art. 1

Having now described my invention, What I claim as new and desire to secure by Letters Patent, is:

l. A vehicle brake equipment comprising manually controlled means for eflecting application and release of the brakes associated with the vehicle wheels, additional means eifective while the is conditioned to cause application of the brakes for effecting release of the brakes. and reapplication of the brakes on a vehicle wheel, means operatively responsive to the slipping of a, vehicle wheel, and

means operated in response to the operation of the wheel-slip responsive means for effecting operation of the said additional means to efiect release of the brakes on the slipping wheel and so controlled thereafter by the degree of application 'of the brakes on the slipping wheel as to cause operation of the additional means to effect reappl-ication of the brakes on the slipping wheel only after the application of the brakes on the slip ping. wheel has been reduced below a certain uniform. degree.

2. A vehicle brake equipment comprising a brake cylinder, manually controlled means for causing fluid under pressure to be supplied to and released from the brake cylinder to efiect application and release of the brakes respectively associated with the vehiclewheels, valve means operative to cut off the supply of fluid under pressure to the brake cylinder as effected under the control of the manually controlled means and to vent fluid under pressure from the brake cylinder, means operatively responsive to the slipping of a vehicle wheel, and means so controlled by the wheel-slip responsive means as to cause the said valve means to operate to vent fluid under pressure from the brake cylinder when a vehicle Wheel begins to slip and effective thereafter independently oi the wheel-slip responsive means and as long as the pressure in the brake cylinder exceeds a certain uniform pressure for causing said valve means to continue to vent fluid under pressure from the brake cylinder.

3. A vehicle brake equipment comprising a brake cylinder, manually controlled means for causing fluid under pressure to be supplied to and released from the brake cylinder to efl'ect application and release of the brakes respectively associated with the vehicle wheels, valve means operative to cut off the supply of fluid under pressure to the brake cylinder as effected under the control of the manually controlled means and to vent fluid under pressure from the brake cylinder, means operatively responsive to the slipping of a vehicle wheel, and means controlled bythe Wheel-slip responsive means for causing the valve means to vent fluid under pressure from the brake cylinder when a vehicle wheel begins to slip and controlled thereafter independently of the wheel-slip responsive means by the pressure in the brake cylinder for causing the valve means to operate to its normal condition permitting the resupply of fluid under pressure to the brake cylinder under the control of the manually controlled means only after the pressure in the brake cylinder has been reduced below a certain uniform pressure.

4. A vehicle brake equipment comprising a rake cylinder, manually controlled means for causing fluid under pressure to be supplied to and released from the brake cylinder to effect application and release respectively .of the brakes associated with the vehicle wheels, additional means for releasing fluid under pressure from the brake cylinder and effecting the resupply of fluid under pressure to the brake cylinder while the manually controlled means is conditioned to supply fluid under pressure to the brake cylinder,

means operatively responsive to the slipping of a' vehicle wheel, and fluid pressure responsive means for controlling the operation of the additional means, said fluid pressure responsive means being operated initially in response to the operation of the wheel-slip responsive means for causing the additional means to release fluid under pressure from the brake cylinder and controlled thereafter independently of the wheelslip responsive means by the pressure in the brake cylinder so as tov cause operation of the additional means to effect reapplication of the brakes on the slipping wheel only when the pressure in the brake cylinder reduces below a certain uniform pressure.

5. A vehicle brake equipment comprising a brake cylinder, manually controlled means for causing fluid under pressure to be supplied to and releasedfrom the-brake. cylinder to eflect application and release respectively of the brakes'associated with the'vehicle wheels, additional means for effecting release of fluid under pressure from the brake cylinder and resupply of fluid under I 'pressure from the brake cylinder while the manually controlled means is conditioned to supply fluid under pressure to the brake cylinder, means operatively responsive to the slipping of a vehicle wheel, fluidpressure responsive means normally unresponsive to the pressure in the brake cylinder, and means controlled by the wheel-slip responsive means and effective when a vehicle Wheel begins to slip for causing said fluid pressure responsive means to operate to cause operation of the additional means to release fluid under pressure from the brake cylinder and to condition the fluid pressure responsive means so as to be responsive to the pressure in the brake cylinder so that it thereafter remains effective to cause the additional me'ans'to continue to vent fluid under pressure from the brake cylinder independently of the wheel-slip responsive means as long as the pressure in the brake cylinder exceeds a certain uniform pressure.

6. A vehicle brake equipment comprising a brake cylinder, means operative to cause fluid under pressure to be supplied to and released from the brake cylinder to effect application and release respectively of the brakes associated with 'the vehicle wheels, valve means normally conditioned to establish communication through which fluid under pressure is supplied to the brake cylinder and operative to close said supply communication and vent fluid under pressure from the brake cylinder, a valve device including a chamber and an operating abutment normally biased to a certain position and operative out of the normal position thereof in response to a fluid pressure in the chamber exceeding a certain uniform low pressure, a valve operated by said abutment and effective in the normal position of the abutment to close communication between the brake cylinder and the chamber of said valve device and effective to establish communication between the brake cylinder and said chamber upon operation of the abutment out of its normal position, said valve device being efiective when the abutment thereof is operated out of its normal position' to cause operation of said valve means to vent fluid under pressure from the brake cylinder, and means responsive to the slipping of a vehicle wheel for causing fluid under pressure to be supplied to the chamber of said valve device to initiate operation of the abutment out .of its normal position,'said abutment being thereafter maintained out of its normal position by the pressure in the brake cylinder as long as the brake cylinder pressure exceeds said certain uniform low pressure, independently of the wheel-slip responsive means.

'7. A vehicle brake equipment comprising a brake cylinder, valve means normally in a position to establish communication through which fluid under pressure is supplied to the brake cylinder to effect application of the brakes and operative out of said positionto close said communication and vent fluid under pressure from the brake cylinder, a valve device for controlling the operation of the valve means, means responsive to the slipping of a vehicle wheel associated with the brake cylinder, and means controlled by the wheel-slip responsive means to cause operation of the valve device'resulting in operation of the valve means to vent fluid under pressure from the brake cylinder and effective to render said sure in the brakecylinder independently of the wheel-slip responsive means.

8. A vehicle brake equipment comprising a brake cylinder, valve means normally establishing communication through which fluid under pressure is supplied to the brake cylinder to effect application of the brakes and release of the brakes and operative to a difierent position to close said-communication and to vent fluid under pressure from the brake cylinder, a valve device for controlling the operation of the valve means, an electroresponsive device for effecting operation of the valve device to cause the valve means to vent fluid under pressure from the brake cylinder, and means rendered subject to brakecylinder pressurewhen the valve device is operated to cause the valve means to vent fluid under pres sure from the brake cylinder for thereafter maintaining the valve device ei fective to cause the valve'means to continue'to vent fluid under pressure from the brake cylinder as long as the pressure in thebrake cylinder exceeds a. certain uni form'low pressure independently of the electroresponsive means. I

9. A vehicle brake equipment comprising means for efi'ecting'application and release of'th'e' brakes associated with a vehicle wheel, a device having an element rotatable according to the speed of rotation of the vehicle wheel and a rctary inertia element associatedwith-the rotary element'and having a normal position relative thereto, said inertia element being shiftable out of its normalp'osition rotatively ahead of the rotary elementwhen the vehicle wheel decelerates while slipping and shiftable out of its normal position rotatively. behind the rotary element when the vehicle wheel accelerates while slipping, means controlled by the relative rotary movement between" the rotary element and the rotary inertia element for causing release of the brakes on the vehicle'wheel while the first said means is conditioned to cause application of the brakes thereon, and means normally-unresponsive to the pressure in the brake cylinder adapted to be rendered responsiveto the pressure in the brake cylinder upon the first relative rotary movement between the rotary'element and the rotary inertia element and eifective to cause said last means to continue releasing the brakes notwithstanding the momentary return of the rotary inertia element to its normal position with respect to the rotary element when a slipping vehicle wheel changes from deceleration to acceleration While slipping.

10. A vehicle brake equipment comprising means for effecting application and release of the valve device controllable thereafter bythe pres brakes associated with a vehicle wheel, additional after control the rate of reapplication of the brakes on said wheel.

11. A vehicle brake equipment comprising a brake cylinder, means providing a communication through which fluid under pressure is supplied to and released from the brake cylinder to effect application and release respectively of the brakes associated with a vehicle wheel, valve.

means operative out .of a normal position in which fluid under pressure may be supplied throu h the said communication to the brake cyli'nder to a difierent position in which the said communication is closed and fluid under pressure is vented from the brake cylinder, .a second valve means normally in a position to enable the rapid supply of fluid under pressure through the said communication and operative to a different position to restrict the rate of sup-ply of fluid under pressure through the said communication, and means responsive to the slipping of a vehicle wheel for controlling the operation of both of said valve means.

12. A vehicle brake equipment comprising a brake cylinder, means providing a communication through which fluid under pressure is supplied to and released from the brake cylinder to effect application and release respectively of the brakes associated with a vehicle wheel, valve means operative out of a normal position in which said communication isopen to a difierent position in which said communication is closed and a different communication is established through which fluid under pressure is vented'from the brake cylinder, .a second valve means normally in a position to enable the rapid supply of fluid under pressure through said communication to the brake cylinder and operative to a different position to restrict the rate of supply of fluid under pressure through the said communication to the brake cylinder, means responsive to the slipping of the vehicle wheel,-and means controlled by the wheel-slipresponsive means for effecting operation of the first valve means to vent fluid under pressure from the brake cylinder and effective thereafter independently of the wheelslip responsive means to cause the first valve means to vent fluid under pressure from the brake cylinder as long as the pressure in the brake cylinder exceeds a certain uniform low pressure, said last means being effective when operated in response to the control of the wheel-slip responsive means to effect operation-of the said second valve means toa position for restricting the rate of supply of fluid under pressure through the said communication to the brake cylinder.

13. A vehicle brake equipment comprising a brake cylinder, means providing a communication through which fluid under pressure is supplied to and released from the brake cylinder to eifect application and release respectively of the brakes associated with a vehicle wheel, valve means normally in a position to open said communication and operative to a position to close said communication and vent fluid under pressure from the brake cylinder, a second valve means normally in a position to enable the rapid supply of fluid under pressure through the said communication to the brake cylinder and operative to a different position to restrict the rate of supply of fluid under pressure to the brake cylinder, means operative in'response to the slipping of the vehicle wheel, means controlled by the wheel-slip responsive means and operated in response to the initiation of slipping of the vehicle wheel for causing operation of the rst said valve means to vent fluid under pressure from the brake cylinder, and means operatively conditioned in response to the operation of .said last means .to maintain the last said means in position to cause the first said valve means to vent fluid under pressure from the brake cylinder as long as the pressure in the brake cylinder exceeds a certain uniform low pressure and effective to control the supply of fluid under pressure to the said second valve means to cause it :to operate to its said :difierent position wherein it restricts the rate .of resupply oi fluid under pressure through the said communication to the brake cylinder.

14:. In a vehicle :brake equipment comprising a brake cylinder, means providing a communication through which fluid under pressure is supplied to and released from the brake cylinder to effect application and release respectively of the brakes associated with a vehicle wheel, means operative in response to the initiation of slipping of the vehicle wheel and controlled thereafter by fluid pressure :in the brake cylinder to cause fluid under pressure to be vented from the brake cylinder during an application of the brakes until the pressure in the brake cylinder reduces below a predetermined uniform low pressure, and means normally conditioned to permit the rapid supply of fluid ,under pressure through the communication to the brake cylinder adapted to beconditioned in response to the operation of the last said means upon slipping of the vehicle wheel .to thereafter restrict the rate of supply of fluid under pressure through the communication to the brake cylinder.

15. A vehicle brake equipment comprising a brake cylinder, means providing :a communication through which fluid under pressure is supplied to and "released from the brake cylinder :to effect application and release respectively of the brakes a'ssoc-iated with a vehicle wheel/means operative in response to the slipping of the vehicle wheel to close said communication and vent fluid under pressure from the brake-cylinder and effective thereafter to restore said communication, and means normally conditioned to permit the rapid supply of fluid under pressure through the said communication to the brake cylinder and :qperatively conditioned in response to the slipping of avehicle wheel to restrict the rate of re upply of fluid under pressure through said communication to the brake cylinder.

16. A vehicle brake equipment comprising a brake cylinder, means providing a communication through which fluid under pressure is supplied to and released from the brake cylinder to effect application and release respectively ,of the brakes associated with a vehicle wheel, valve means controlling the supply of fluid under pressure through the said communication to the brake cylinder effective normally to ,permit a certain rate of supply and when in ,a different position to permit a lesser rate of supply through the communication, meansoperative in response to theslipping of a vehicle wheel for effectingoperation of the valve means to its said different position, and means for maintaining said valve means in said different position independently of the wheel-slip responsive means. a

1.7. A vehicle brake equipment comprising a brake cylinder, means providing a communication through which fluid under pressure is supplied to and released from the brake cylinder to eflect application and release respectively of the brakes associated with a vehicle Wheel, valve means controlling the supply of fluid under pressure through the said communication to the brake cylinder effective normally to permit .a certain rate of supply and when in a diiferent position to permit a lesser rate of supply through the communication, means operative in response to the slipping of a vehicle wheel for eifecting operation of the valve means to its said different position, and means for maintaining said valve means in its said different position for a'limited time independently of the operation of the wheelslip responsive means in response to cessation of slipping of the vehicle wheel.

18. In a vehicle brake equipment comprising a brake cylinder, means providing a communication through which fluid under pressure is supplied to and released from the brake cylinder to effect application-and release respectively of the brakes associated with the vehicle wheel, fluid pressure operated valve means having a chamber and operative in response to supply of fluid under pressure to the said chamber from one position in which it permits a rapid supply of fluid under pressure through the communication to the brake cylinder to a different position in which a lesser rate of supply of fluid under pressure through the communication to the brake cylinder is permitted. means operative upon the initiation of slipping of a vehicle wheel for rapidly supplying fluid under pressure to said chamber to cause operation of the valve means to its said different position, and means for venting fluid under pressure from said chamber at a restricted rate.

19. A vehicle brake equipment comprising a brake cylinder, means providing a communication through which fluid under pressure is supplied to and released from the brake cylinder to eflect application and release respectively of the brakes associated with the vehicle wheel, fluid pressure operated valve means having a chamber and 0perative in response to the charging of said chamber with fluid at a relatively low pressure from one position in which it permits the supply of fluid under pressure through the communication to the brake cylinder at a relatively rapid rate to a diiferent position in which it permits the supply of fluid under pressure through the communication to the brake cylinder at a relatively slow rate, means operative in response to the initiation of slipping of a vehicle wheel for causing said chamber to be rapidly charged with fluid under pressure from the brake cylinder at the time the slipping of the wheel begins to cause operation of the valve to its said different position, and means for venting fluid under pressure from said chamber at a restricted rate for maintaining sufficient pressure in said chamber to maintain the valve means in its said different position for a limited time.

20. In a vehicle brake equipment, means providing a communication through which fluid under pressure may be supplied at a certain rate to effect application of the brakes on a vehicle wheel, valve means normally in a position to permit the supply of fluid under pressure through said communication at the said certain rate and operative to a different position in which it is effective to prevent the supply of fluid under pressure through said communication except at a rate lower than said certain rate, and means effective in response to the slipping of the vehicle wheel to cause operation of the said valve means to its said different position.

21. In a vehicle brake equipment, means providing a communication through which fluid under pressure may be supplied at a certain rate to effect application of the brakes on a vehicle wheel, valve means normally in a position to permit the supply of fluid under pressure through said communication at the said certain rate and operative to a different position in which it is effective to prevent the supply of fluid under presure through said communication except at a rate lower than said certain rate, means efiective in response to the slipping of the vehicle wheel to cause operation of the said-valve means to its said different position, and means efiective to maintain said valve means in its said different position for at least a certain limited time.

22. A vehicle brake equipment comprising a brake cylinder, means for causing fluid under pressure to be supplied to the brake cylinder and released therefrom to effect application and release of the brakes associated with the vehicle wheel, valve means operative out of the normal position in which it establishes communication through which fluid under pressure is supplied to the brake cylinder to a different position in which it closes the supply communication and estab lishes a different communication through which fluid under pressure is released from the brake cylinder, a magnet valve device for controlling the operation of said valve means, fluid pressure operated switch means controlling said magnet valve device, and means responsive to the slipping of a vehiclewheel effective when a vehicle wheel begins to slip to cause operation of the fluid pressure operated switch out of the normal position to a different position, said fluid pressure operated switch device being rendered subject to brake cylinder pressure once it is operatedout of its normal position so that the switch device is.

thereafter maintained out of its normal position as long as the brake cylinder pressure exceeds a certain uniform low pressure, independently of the control of the wheel-slip responsive means.

23. A vehicle brake equipment comprising a brake cylinder, means operative to cause fluid under pressure to be supplied to and released from the brake cylinder to effect application and release respectively of the brakes associated with vehicle wheels, a normally deenergized magnet valve device effective when deenergized to cause communication to be maintained through which fluid under pressure is supplied to the brake cylinder and effective when energized to cause said communication to be closed and another communication to be established through which fluid under pressure is vented from the brake cylinder, means effective to cause energization of said magnet valve device when a vehicle wheel begins to slip, and means normally unresponsive to brake cylinder pressure adapted to be rendered responsive to brake cylinder pressure once a vehicle wheel slips for maintaining said magnet valve device energized as longas the brake cylinder pressure exceeds a certain uniform low pressure to be supplied toand released from the brake cylinder to effect application and release respectively of the brakes associated with a vehicle Wheel, a normally deenergized magnet valve device effective when deenergized to cause communication to be maintained through which fluid under pressure is supplied to the brake cylinder and effective when energized to cause the said communication to be closed and another communication to be established through which fluid under pressure is vented from the brake cylinder,

a fluid pressure operated switch device having a chamber and operative upon the supply of fluid under pressure to said chamber to cause energization of said magnet valve device, and a valve operated in response to the supply of fluid under pressure to the chamber of said switch for estabunder the controlof said valve and maintained in an operative position to maintain energization of said magnet Valve device independently of the interruption of the supply of fluid under pressure to said chamber under the control of the wheel- 5 slip responsive means.

CLYDE C. FARMER. 

